One or more embodiments of the present invention pertain to fabrication of electronic devices such as integrated circuits; more specifically, one or more embodiments of the present invention relate to systems, apparatuses, and methods for electroless deposition (ELD) of metals such as metallization layers.
Electroless deposition is frequently used in the fabrication of electronic devices. The process is important for applications requiring deposition of metal on substrates for layers to form integrated circuits. Electroless deposition processes can readily proceed on certain activated and/or catalytic surfaces such as metal, metal alloy, or other electrically conductive surfaces.
As such, electroless deposition solutions may be or may become unstable solutions if the properties of the solution or the conditions of use of the electroless deposition solutions change. Although the usual intention of electroless deposition is to achieve metal or metal alloy deposition exclusively on the substrate, electroless deposition of the metal or the metal alloy can occur in places other than on the substrate such as on metal particles, semi-conductive particles, and/or imperfections in the deposition system chamber walls. Consequently, plating other than on the substrate is often to be expected.
Electroless deposition systems that recycle at least a portion of the electroless deposition solution may dislodge deposited metal particles and carry them anywhere in the recycling system, hence further deposition may occur on these metal particles at any place in the system. For these and/or other reasons, electroless deposition systems are susceptible to a phenomena referred to here as “plating out.”Plating out is a catastrophic deposition of the metal other than on the substrate in an electroless deposition chamber. Catastrophic is defined here to mean that either the rate of deposition is rapid and/or the deposition occurs in such a massive amount that metal particles form and accumulate inside the electroless deposition system. Plating out also includes having the metal form particles in the electroless deposition solution. When formed as small metal particles, the particles may be suspended, at least temporarily, in the electroless deposition solution. The metal particles may grow in size so that the metal particles settle in various regions of the electroless deposition system. Previous efforts to avoid the problems of plating out have been unsuccessful.
The present inventor has made one or more developments that may be pertinent to electroless deposition technology such as that for electronic devices. The one or more developments may have the potential to alleviate problems such as plating out for one or more electroless deposition processes.